1. Field of the Invention
This invention relates to an edible, shelf-stable legume and/or cereal food product that is nutritious, tasty and palatable. This invention also relates to a method of processing legumes and cereals, alone or in combination, to produce the food product.
2. Description of the Background
The nomenclature of "field-dried legumes" is generally intended to describe mature dried seeds of many types of beans, peas, and lentils grown as field crops, that are broadly consumed by man across the world. Although soybeans (Glycine max L. Merr.) and peanuts (Arachis hypogaea L.), which are also known as "ground nuts", are classified as legumes, the energy for the young plant in these seeds is stored primarily in the form of oil. In contrast, the oil content in "field-dried legumes" is low, usually under 3 wt %, with much of the energy for the seedling being stored in the form of starch, e.g., about 35 to 40 wt %, which is only a minor component of soybeans and peanuts, e.g., about 1 wt % and 5 wt %, respectively.
In the present context, mature, field-dried legume seeds will simply be referred to as "legumes" to avoid confusion when describing wet or dry processing intermediates and products. In the context of this invention, the term legumes encompass low-fat, high-starch legumes, as well as mixtures thereof with high-oil type legumes, provided that the total amount of oil contributed by the high oil type legume to the product does not interfere with its processing or achievement of desirably textured products.
Legumes include many genuses and species, among which are the following. Phaseolus vulgaris L. is perhaps the best known group of beans in the Americas and Northern Europe. This group of beans includes common field bean species like black, cranberry, Great Northern, kidney, navy, pink, pinto and large and small white beans. The chickpea, Cicer arietinum L., also known as the garbanzo bean and Bengal gram, is a basic food in eastern Mediterranean countries, Northern Africa and Southwest Asia. The black-eye pea, Vigna unguiculata, is a major protein source in Central Africa, which was brought to the New World where milder-flavor varieties like the cream pea are also used. The mung bean or green gram, Vigna radiata, is best known in the United States as the source of bean sprouts, but is consumed in many additional ways in Eastern and Southern Asia. Vicia faba L., known as the faba bean, broad bean, horsebean, and occasionally as the field bean, has long been a food of the "poorest of the poor of the world", and is used in Eastern Europe, and Northern Africa. Other beans of widespread use are the pigeon pea and red gram of Egypt, India and Brazil or Cajanus cajan sometimes growing as a perennial bush; the Kesari dahl or chicking vetch or Lathyrus sativus L., grown and eaten during droughts in India that may cause nervous paralysis of the lower limbs among young men if not properly prepared; the lima bean or Phaseolus lunatus L. requiring thorough cooking to inactivate hemagglutinin; and the escumite or tepary bean or Phaseolus acutifolius Gray var of Northern Mexico and Southwest United States, highly toxic in the raw state. Other commonly-used dry legumes include lentils such as Lens culinaris L. and L. esculenta L., and dry green and yellow peas or Pisum sativum L., frequently used in North America and Northern Europe.
As a group, legumes are a rich source of nutrients, generally containing about 17 to 25 wt % protein on a dry weight basis, and about 58 to 68 wt % carbohydrates, much of which are in complex forms favored by nutritionists. Further, field beans, peas and lentils are sources of water-soluble vitamins, potassium and magnesium, dietary fiber and natural antioxidants.
Advantages of legumes include short growing periods enabling their production in areas with limited frost-free days and/or short rainy seasons, relatively high protein yield per unit of land, and long-term storability of the seeds given their low fat content and natural resistance to insects.
Legumes, however, also have disadvantages. Many varieties of beans, including those used in the United States, have high levels of trypsin inhibitors, hemagglutinins and other toxic compounds or anti-growth factors that must be removed by leaching and/or deactivation by cooking. In addition, legumes contain about 3 to 7 wt % flatulence oligosaccharides or sugars such as raffinose, stachyose, verbascose, and ajugose, among others. These oligosaccharides are not digested and absorbed in the human stomach or small intestine due to a lack of suitable enzymes. They pass into the large intestine, where they are metabolized by random colon bacteria, sometimes producing odiferous gases and discomfort.
Beans are often unpopular in sophisticated societies due to their producing intestinal discomfort and gas venting, and because they are a staple of the poor. In addition, beans typically require lengthy cooking. Their cooking time may, however, be reduced by presoaking, a process that also leaches out some of the stronger flavored components and hull pigments. Seeds of most varieties, however, develop a "hard shell" during storage, a condition in which water uptake is greatly retarded and the cooking time of the bean is significantly increased as the crop ages. Unfortunately, the areas of the world where beans are the last resort of storable, concentrated food protein often are also faced with shortages of water, and especially fuel to cook them adequately for their safe use.
Cereal crops such as wheat, corn or maize, rice, barley, oats, sorghum and millet also are storable and are widely used as food stuffs. Although their protein content, generally about 8-13 wt %, and up to 19 wt % for oats, is lower than that of legumes, cereal grains are eaten in greater quantities than legumes or soybeans and are the major sources of plant protein in the world's human diet. Cereal seeds account for as much as 70 wt % of the total caloric intake of humans in some regions.
The protein contained in cereal seeds includes a good supply of the sulfur-containing essential amino acids methionine and cystine, but is otherwise nutritionally unbalanced due to an insufficient content of the essential amino acid lysine. In contrast, the protein of legumes and soybeans is high in lysine but low in the sulfur-containing amino acids. Nutritionists have found that cereal grains and either legumes or soybeans optimally complement one another when mixed in an approximate proportion of about 7:3 wt:wt; this results in a total dietary protein content that has the approximate nutritional quality of meat protein.
Given the high nutritional quality that a mixture of legumes and cereals provides, it would be highly desirable to have a ready-to-eat, shelf-stable precooked food product made of legumes and/or cereals that would be inexpensive to prepare and could be made available to the population at large, including the poorest segments of the population.